This is a supplement to Research Grant EY 02526. The objectives of EY 02526 are to continue the studies of the pathophysiology of the circulation of the retina, choroid, and distal segment of the optic nerve. The purpose of this supplement is to continue and expand the input of biomedical engineering and computational expertise required in the experimental design and data analysis. In effect it formalizes an informal collaboration of eight years duration. Also, because the Principal Investigator is now a department chairman and will have less time in the future for research, it is especially necessary at this time to increase the technical input in order to optimize his available time and maintain the high level of productivity of this research program. Choroidal blood flow data obtained on experimental animals using the method of indocyanine green clearance will be analyzed by computer (nonlinear regression). Changes in perfusion pressure, light, blood gases, sympathetic manipulation, and various diabetic interventions will be studied with the aim of duplicating conditions in glaucoma, hypotony, hypertension, macular degeneration, and diabetic retinopathy. The hydrogen clearance method for measuring blood flow in the anterior optic nerve will be studied mathematically to confirm its validity. Then experimental data obtained following the same changes as above will also be analyzed by computer modelling. Finally, non-invasive on-line methods will be devised for analyzing vessel size, reactivity and blood oxygen saturation in retinal arteries and veins, centrally and peripherally, again following the above changes but this time using optical density profiles measured virtually continuously with fiber optic devices to be specially developed. Again the data will be computer fitted to the appropriate model to give vessel size and oxygen saturation.